Climate scenarios, as summarized by the Intergovernmental Panel on Climate Change (IPCC), project that mean global temperatures are likely to increase by 1.4-5.8°C over the present century. As a high-latitude country, warming in Canada would likely be more pronounced (Figure 1). Temperature increases would vary across the country, with certain regions including the North and the southern and central Prairies warming more than others. Warming is also projected to vary on a seasonal basis, being greatest in winter, and on a daily basis, with nights warming more than days. Changes in precipitation patterns, changes in climate variability, and shifts in the frequency and intensity of extreme climate events would accompany warming. Since these changes would not be felt uniformly across the country, impacts would vary regionally.

Figure 1: Annual temperature projection for 2080s, based on Canadian Global Coupled Model 2-A21. Courtesy of Canadian Institute of Climate Studies.

There is growing evidence that climate change is already occurring. At the global scale, average surface temperatures rose about 0.6°C over the 20th century. Warming of minimum and maximum temperatures has also been detected in Canada. Correspondingly, there have been decreases in sea-ice cover, shifts in species distributions and an increase in global average sea level. The IPCC has also concluded that there have very likely been increases in annual precipitation, heavy precipitation events, cloud cover and extreme high temperatures over at least the last 50 years.